The object of this invention is a tyre removal tool for a tyre removing machine and a tyre changing machine equipped with such a tool.
The invention relates to equipment for tyre service specialists and, in particular, to tyre removing machines, that is, machines for removing tyres from wheel rims.
Usually, these tyre removing machines are also used to fit the tyre to the wheel rim.
In light of this, the invention also relates to tyre changing machines for fitting and removing tyres to and from the respective wheel rims.
Whatever the case, for brevity, the term “tyre removing machine” will be used to also denote tyre changing machines which can fit tyres in addition to removing them.
The tyre removing machine comprises a rotary support, also known as “turntable”, for the wheel.
The tyre removing machine also comprises a frame to which an arm is movably connected in order to move towards and away from the wheel positioned on the rotary support.
The tyre removing machine further comprises a tyre removal tool connected to a free end of the arm. More specifically, the tool has a first end which is connected to the arm.
The removal tool has the form of a lever and is adapted for insertion between the tyre bead and the edge of the wheel rim to facilitate extraction of the bead from the rim during removal of the tyre from the wheel rim.
It should be noted that even when the tyre is being fitted to the rim, the tool (which for convenience will nevertheless be referred to as “removal tool”) is inserted between the tyre bead and the edge of the wheel rim to facilitate insertion of the bead into the rim.
More specifically, the procedure commonly followed to remove a tyre from a respective wheel rim is as follows.
First of all, the tool is positioned near the tyre bead. The tool is then inserted between the edge of the wheel rim and the tyre bead by moving the tool towards the wheel rim. This movement preferably occurs in a direction parallel to the axis of the wheel rim, which corresponds to the axis of the wheel.
At that position, the tool is moved in such a way that a second end of it grasps a portion of the bead.
Next, the tyre bead is extracted from the wheel rim by moving the tool away from the wheel rim. This movement preferably occurs along a direction parallel to the axis of the wheel rim itself.
Preferably, once the bead has passed the edge of the wheel rim, the bead is moved towards the axis of the wheel rim. This reduces the mechanical stress applied to the bead during the subsequent stages.
Next, the wheel rim is set in rotation about its axis while keeping the bead out of the wheel rim.
When removing the tyre from the wheel rim (and more generally speaking, when fitting and removing it), the following are the three requirements to be met:
i) simplifying the operator's work by reducing the effort required of, and the direct action to be taken by, the operator;
ii) limiting the risk of damaging the tyre;
iii) avoiding damage to the wheel rim.
As regards the risk of damaging the tyre, the need to reduce the mechanical stress applied to the tyre bead when the bead is held in the extracted position has been known for some time.
In light of this, several technical solutions have been developed where the above mentioned operations have been substantially automated with the aid of user-operated actuators.
Patent document EP1177920 in the name of the same Applicant as this invention describes an automatic tyre removing machine where the tool is pivoted to the arm in such a way that it can oscillate between two or more operating positions.
In particular, when the tool is inserted between the edge of the wheel rim and the tyre bead, the removal tool is oriented in a first operating position relative to the arm. When the bead is extracted from the rim, on the other hand, the removal tool is oriented in a second operating position relative to the arm (rotated relative to the first operating position).
The rotation of the tool relative to the arm (from the first operating position to the second and vice versa) is carried out by an actuator, which the user must operate at the right moment and which is designed to reduce the mechanical stress the tyre bead is subjected to when it is in the extracted position.
Further, also according to the teachings of EP1177920, the second end of the removal tool (that is, the free end) is hook shaped. This allows the tool to grasp the tyre bead when the tool is inserted between the bead and wheel rim.
This solution has three disadvantages, however.
A first disadvantage is due to the fact that inserting the hook-shaped tool between the edge of the wheel rim and the tyre bead creates the risk of damage, at least to the bead.
A second disadvantage is that the machine is complex and although it allows the user to save physical effort, it nevertheless requires a great deal of care and skill of the user to control riot only the movement of the arm (and of the tool connected thereto) but also the movement of the tool relative to the arm.
A third disadvantage is the complexity and high cost of the tool drive system, which is made up of several different parts.
Patent document EP1593533, in the name of the same Applicant as this invention, is an example of an improvement to the technical solution provided by patent document EP1177920. In effect, EP1593533 proposes a technical solution where the tool is connected to the arm by a kinematic mechanism (more specifically, a four-bar linkage) which guides its movement according to a predetermined path.
This simplifies the user's task since there is no need for combined operation of the actuator which moves the arm (and the tool connected thereto) and the actuator which moves the tool relative to the arm, and all the user has to do is to operate an actuator which drives the tool through the agency of the kinematic mechanism, thereby obtaining a tool movement along a trajectory which reduces the mechanical stress applied to the bead when the bead is being extracted and when it is in the extracted position (during the subsequent step of rotating the wheel rim).
Nevertheless, patent EP1593533 still has the disadvantage of creating a significant risk of damaging the tyre bead (and even the edge of the wheel rim) when the hook-shaped tool is inserted between the rim edge and the bead.
Another example of a tyre removing machine is described in patent document EP1714807B1, which proposes a technical solution which is a variation on the use of a four-bar linkage for connecting the tool to the arm.
In a first embodiment, the tool (which is still an elongate element having a hook-shaped end) is hinged to a lever which is in turn hinged to the arm.
In this case, tool movement during the steps of insertion and extraction is controlled by turning this lever.
In a second embodiment proposed by patent EP1714807B1, the tool is pivoted to a slot formed on the arm so as to be able to roto-translate relative to it.
Nevertheless, even patent EP1714807B1 has the disadvantage of creating a significant risk of causing damage to the tyre bead and certainly also to the edge of the wheel rim (which the tool has to rest on) when the hook-shaped tool is inserted between the rim edge and the bead.
Patent document EP1459913 discloses a device for mounting and demounting tyre which has the drawbacks mentioned above.